Guarantor and Non-Guarantor Financial Information - Balance Sheet (Details) - USD ($) $ in Thousands | Jun. 30, 2016 | Sep. 30, 2015 | Jun. 30, 2015 | Sep. 30, 2014 |
Current assets: | | | | |
Cash and cash equivalents | $ 907,032 | $ 729,384 | $ 774,540 | $ 360,307 |
Short-term investments | 49,565 | 45,543 | | |
Accounts receivable, net of reserve | 351,317 | 445,948 | | |
Inventories | 128,885 | 128,541 | | |
Prepaid expenses and other | 79,021 | 64,475 | | |
Assets held for sale | 21,772 | | | |
Deferred income taxes | | 17,206 | | |
Current assets of discontinued operations | 80 | 8,097 | | |
Total current assets | 1,537,672 | 1,439,194 | | |
Investments | 99,898 | 104,354 | | |
Property, plant and equipment, net | 5,306,434 | 5,563,170 | | |
Other assets | 32,515 | 40,524 | | |
Total assets | 6,976,519 | 7,147,242 | | |
Current liabilities: | | | | |
Long-term debt due within one year | 39,234 | 39,094 | | |
Accounts payable | 92,692 | 108,169 | | |
Accrued liabilities | 194,645 | 197,557 | | |
Current liabilities of discontinued operations | 38 | 3,377 | | |
Total current liabilities | 326,609 | 348,197 | | |
Noncurrent liabilities: | | | | |
Long-term debt | 493,150 | 492,443 | | |
Deferred income taxes | 1,358,093 | 1,295,916 | | |
Other | 93,221 | 110,120 | | |
Noncurrent liabilities of discontinued operations | 3,984 | 4,720 | | |
Total noncurrent liabilities | 1,948,448 | 1,903,199 | | |
Shareholders' equity: | | | | |
Common stock | 11,138 | 11,099 | | |
Additional paid-in capital | 442,883 | 420,141 | | |
Retained earnings | 4,438,748 | 4,648,346 | | |
Accumulated other comprehensive loss | (3,156) | (1,377) | | |
Treasury stock, at cost | (188,151) | (182,363) | | |
Total shareholders' equity | 4,701,462 | 4,895,846 | | |
Total liabilities and shareholders' equity | 6,976,519 | 7,147,242 | | |
Eliminations | | | | |
Current assets: | | | | |
Accounts receivable, net of reserve | (871) | (5) | | |
Prepaid expenses and other | (2,017) | (7,903) | | |
Deferred income taxes | | (4,905) | | |
Total current assets | (2,888) | (12,813) | | |
Intercompany | (1,707,082) | (1,439,161) | | |
Other assets | (10,479) | (8,153) | | |
Investment in subsidiaries | (5,849,057) | (5,851,341) | | |
Total assets | (7,569,506) | (7,311,468) | | |
Current liabilities: | | | | |
Accounts payable | (856) | (5) | | |
Accrued liabilities | (2,032) | (11,103) | | |
Total current liabilities | (2,888) | (11,108) | | |
Noncurrent liabilities: | | | | |
Deferred income taxes | (11,479) | (13,058) | | |
Intercompany | (1,705,982) | (1,435,961) | | |
Total noncurrent liabilities | (1,717,461) | (1,449,019) | | |
Shareholders' equity: | | | | |
Common stock | (100) | (100) | | |
Additional paid-in capital | (47,919) | (46,173) | | |
Retained earnings | (5,799,382) | (5,801,212) | | |
Accumulated other comprehensive loss | (1,756) | (3,856) | | |
Total shareholders' equity | (5,849,157) | (5,851,341) | | |
Total liabilities and shareholders' equity | (7,569,506) | (7,311,468) | | |
Guarantor/Parent | Reportable Legal Entities | | | | |
Current assets: | | | | |
Cash and cash equivalents | (920) | (838) | (877) | (2,050) |
Accounts receivable, net of reserve | 39,698 | 152 | | |
Prepaid expenses and other | 7,997 | 20,018 | | |
Deferred income taxes | | 2,834 | | |
Total current assets | 46,775 | 22,166 | | |
Investments | 12,848 | 12,871 | | |
Property, plant and equipment, net | 61,989 | 55,902 | | |
Intercompany | 15,982 | 15,875 | | |
Other assets | 10,713 | 8,387 | | |
Investment in subsidiaries | 5,645,245 | 5,623,754 | | |
Total assets | 5,793,552 | 5,738,955 | | |
Current liabilities: | | | | |
Accounts payable | 80,926 | 80,673 | | |
Accrued liabilities | 20,936 | 10,688 | | |
Total current liabilities | 101,862 | 91,361 | | |
Noncurrent liabilities: | | | | |
Intercompany | 971,750 | 733,008 | | |
Other | 18,478 | 18,740 | | |
Total noncurrent liabilities | 990,228 | 751,748 | | |
Shareholders' equity: | | | | |
Common stock | 11,138 | 11,099 | | |
Additional paid-in capital | 442,883 | 420,141 | | |
Retained earnings | 4,438,748 | 4,648,346 | | |
Accumulated other comprehensive loss | (3,156) | (1,377) | | |
Treasury stock, at cost | (188,151) | (182,363) | | |
Total shareholders' equity | 4,701,462 | 4,895,846 | | |
Total liabilities and shareholders' equity | 5,793,552 | 5,738,955 | | |
Issuer Subsidiary | Reportable Legal Entities | | | | |
Current assets: | | | | |
Cash and cash equivalents | 892,476 | 693,273 | 755,070 | 329,655 |
Short-term investments | 49,565 | 45,543 | | |
Accounts receivable, net of reserve | 269,495 | 374,383 | | |
Inventories | 88,438 | 88,010 | | |
Prepaid expenses and other | 33,403 | 6,713 | | |
Assets held for sale | 21,772 | | | |
Deferred income taxes | | 19,277 | | |
Total current assets | 1,355,149 | 1,227,199 | | |
Investments | 87,050 | 91,483 | | |
Property, plant and equipment, net | 4,840,172 | 5,063,705 | | |
Intercompany | 1,426,888 | 1,192,634 | | |
Other assets | 1,019 | 1,389 | | |
Investment in subsidiaries | 203,812 | 227,587 | | |
Total assets | 7,914,090 | 7,803,997 | | |
Current liabilities: | | | | |
Long-term debt due within one year | 39,234 | 39,094 | | |
Accounts payable | 8,718 | 20,404 | | |
Accrued liabilities | 138,267 | 151,721 | | |
Total current liabilities | 186,219 | 211,219 | | |
Noncurrent liabilities: | | | | |
Long-term debt | 493,150 | 492,443 | | |
Deferred income taxes | 1,321,148 | 1,275,428 | | |
Intercompany | 257,947 | 186,784 | | |
Other | 28,455 | 31,560 | | |
Total noncurrent liabilities | 2,100,700 | 1,986,215 | | |
Shareholders' equity: | | | | |
Common stock | 100 | 100 | | |
Additional paid-in capital | 47,372 | 45,824 | | |
Retained earnings | 5,577,943 | 5,556,783 | | |
Accumulated other comprehensive loss | 1,756 | 3,856 | | |
Total shareholders' equity | 5,627,171 | 5,606,563 | | |
Total liabilities and shareholders' equity | 7,914,090 | 7,803,997 | | |
Non-Guarantor Subsidiaries | Reportable Legal Entities | | | | |
Current assets: | | | | |
Cash and cash equivalents | 15,476 | 36,949 | $ 20,347 | $ 32,702 |
Accounts receivable, net of reserve | 42,995 | 71,418 | | |
Inventories | 40,447 | 40,531 | | |
Prepaid expenses and other | 39,638 | 45,647 | | |
Current assets of discontinued operations | 80 | 8,097 | | |
Total current assets | 138,636 | 202,642 | | |
Property, plant and equipment, net | 404,273 | 443,563 | | |
Intercompany | 264,212 | 230,652 | | |
Other assets | 31,262 | 38,901 | | |
Total assets | 838,383 | 915,758 | | |
Current liabilities: | | | | |
Accounts payable | 3,904 | 7,097 | | |
Accrued liabilities | 37,474 | 46,251 | | |
Current liabilities of discontinued operations | 38 | 3,377 | | |
Total current liabilities | 41,416 | 56,725 | | |
Noncurrent liabilities: | | | | |
Deferred income taxes | 48,424 | 33,546 | | |
Intercompany | 476,285 | 516,169 | | |
Other | 46,288 | 59,820 | | |
Noncurrent liabilities of discontinued operations | 3,984 | 4,720 | | |
Total noncurrent liabilities | 574,981 | 614,255 | | |
Shareholders' equity: | | | | |
Additional paid-in capital | 547 | 349 | | |
Retained earnings | 221,439 | 244,429 | | |
Total shareholders' equity | 221,986 | 244,778 | | |
Total liabilities and shareholders' equity | $ 838,383 | $ 915,758 | | |